This invention relates generally to a semiconductor processing system and, more specifically, to a semiconductor processing system having a processing chamber and a heat source assembly.
Rapid thermal processing (RTP) systems are employed in semiconductor chip fabrication to create, chemically alter or etch surface structures on semiconductor wafers. One such RTP system, as described in U.S. Pat. No. 5,155,336, includes a semiconductor processing chamber and a lamphead or heat source assembly located on the semiconductor processing chamber.
The semiconductor processing chamber may be fitted with a reduced pressure (RP) adapter plate for low pressure operation. The RP adapter plate includes a lower quartz window, an upper quartz window and a strengthening component, which is sandwiched between the lower and upper windows. The strengthening component may be made of stainless steel and comprise two spaced plates and a surrounding ring, which jointly define an enclosed volume. A plurality of tubes are welded into through holes in the plates to form light passageways.
A number of radiant heat sources, such as lamps, are located in the lamphead. The lamps are powered through a wiring collar, which is connected to a power supply controller by heavy-duty electrical cabling. The wiring collar includes numerous terminal block-to-lamp wires and lamp-to-lamp interconnect wires. Assembly and testing of the wiring collar and the lamphead cables can be expensive and time consuming.
During processing, radiation from the lamps radiates through the upper window, the light passageways and the lower window onto a wafer in the processing chamber. In this manner, the wafer is heated to a required processing temperature.
The pressure within the processing chamber, during processing, may be at a subatmospheric pressure. The reduced pressure within the processing chamber results in a negative pressure on the lower surface of the lower window. The pressure within the enclosed volume defined by the plates and the surrounding ring can be reduced to a pressure which is lower than, or near to, the pressure within the processing chamber in order to prevent collapse of the lower window. To this end, a port extends through the surrounding ring and is connected to a pump to reduce the pressure within the enclosed volume defined by the spaced plates and the ring.
In general, the invention is directed to a semiconductor processing system. In one aspect, the invention features an assembly of radiant energy sources having an upper surface and a lower surface. A window forms a seal with the lower surface of the assembly, and a printed circuit board structure forms a seal with the upper surface of the assembly. The printed circuit board structure is configured to distribute power to the radiant energy sources. The window and the printed circuit board structure form an evacuable enclosure including the assembly.
Particular implementations can include one or more of the following features. A base plate may be disposed between the printed circuit board structure and the upper surface of the assembly such that the window, base plate and printed circuit board structure form the evacuable enclosure that includes the assembly. A clamp ring can be used to secure the printed circuit board structure to the base plate. A plurality of o-ring seals can be used to maintain the vacuum integrity of the enclosure.
The printed circuit board structure can include a vacuum barrier layer, a base printed circuit board layer and a socket layer. The base printed circuit board layer has electrically-conductive traces and receptacles to distribute power to the radiant energy sources. The socket layer includes a plurality of receptacles configured to receive the radiant energy sources. The radiant energy sources have a flexible base which is received within one of the receptacles of the socket layer.
In yet another aspect, the invention features a system for use in semiconductor processing, including an assembly of radiant energy sources located within a housing having an upper surface and a lower surface. The printed circuit board structure forms a seal with the upper surface of the housing and distributes power to the radiant energy sources. A window forms a seal with the lower surface of the housing. A cover forms a seal with the printed circuit board structure. The housing, window, printed circuit board structure and cover form an evacable enclosure that encloses the radiant energy sources and a portion of the printed circuit board structure.
This system may further include an o-ring seal located between the cover and the printed circuit board structure.
In another aspect, the invention features an assembly of radiant energy sources located in a housing having an upper surface and a lower surface wherein a printed circuit board forms a seal with the upper surface of the housing. The printed circuit board is configured to distribute power to the radiant energy sources. The window forms a seal with the lower surface of the housing. The housing, window and printed circuit board form an evacuable enclosure.
The system may further include a socket layer having a plurality of receptacles configured to receive the radiant energy sources. The radiant energy sources can include a flexible base having a plurality of electrical connectors configured to receive power from the printed circuit board. Each electrical connector can be disposed within a plug of the flexible base and each socket layer receptacle can be configured to receive one of the plugs such that arcing is prevented. Each plug may have a circumferential notch configured to receive an o-ring to engage an interior surface of a socket layer receptacle. The plug may have a convex surface to engage the interior surface of the socket layer receptacle.
A base plate may be disposed between the printed circuit board and the upper surface of the assembly. A plurality of o-rings can be provided to maintain the vacuum integrity of the enclosure.
In still another aspect, the invention features a semiconductor processing system having a process chamber with a window and a support on which a substrate may be positioned during processing. The system further includes an assembly of radiant energy sources located on a side of the window opposite from that of the support to direct radiant energy through the window and onto a substrate on the support. The printed circuit board structure is located on a side of the radiant energy assembly opposite from that of the window to distribute power to the radiant energy sources. The window and the printed circuit structure are sealed to the radiant energy assembly such that the radiant energy assembly is evacuable to a pressure lower than or equal to a pressure in the process chamber.
In yet another aspect, the invention features a system for the thermal processing of a substrate. The system includes a process chamber having a window. The system also includes an assembly of radiant energy sources and reflectors disposed outside of the process chamber adjacent to the window to direct radiant energy through the window onto a substrate in the process chamber. The printed circuit board structure is located on a side of the assembly opposite from that of the window and is joined to an upper surface of the assembly to distribute power to the radiant energy sources.
The printed circuit board structure and the window can be sealed to the assembly to form an evacuable enclosure. Vacuum pumps may be used to evacuate the housing and the process chamber. The printed circuit board structure can include a vacuum barrier layer, a base printed circuit board layer and a socket layer.
In still another aspect, the invention features a printed circuit board structure for delivering power to an assembly of radiant energy sources of a semiconductor processing system. The printed circuit board structure includes a base printed circuit board layer having electrically-conductive receptacles configured to receive electrical connectors of the radiant energy sources and electrically-conductive traces to deliver power to the electrically-conductive receptacles.
Particular implementations can include one or more of the following features. The printed circuit board structure may include a socket layer having receptacles configured to receive base portions of the radiant energy sources. The socket layer is made of an electrically-insulating material. The base portions of the radiant energy sources are flexible and house a pair of electrical connectors each of which is configured to be received within a respective one of the base printed circuit board layer receptacles. The base portions of the radiant energy sources can include means for preventing arcing between the electrical connectors, and between the electrical connectors and ground. The arcing prevention means is positioned in the socket layer receptacles. The printed circuit board structure may also include a vacuum barrier layer.
Among the advantages of the invention are the following. The need for an RP adapter plate is eliminated, significantly reducing cost. Another benefit of removing the RP adapter is improved energy transfer from the lamphead to the process chamber.
The PCB structure serves two functions: power distribution and lamphead vacuum barrier. Using the PCB structure as part of a vacuum enclosure allows for a simple design. The PCB structure offers other advantages over current wiring collar designs including reductions in cost, size and complexity. The PCB structure is capable of distributing over 200 kilowatts(kw) of power to the lamphead assembly. The temperature of the PCB structure remains within safe material limits to prevent failure. Vacuum integrity is maintained, while minimizing the volume that needs to be evacuated. The main power cables for the lamphead assembly are external to the vacuum enclosure, eliminating the need for vacuum feedthroughs, and reducing outgassing problems and potential electrical arcing locations. Part cost, part count, assembly time, and test time are reduced.
Lamps having flexible bases are provided to accommodate imperfect alignment between lamp housing tubes and socket layer receptacles. The flexible base allows the lamp to be plugged directly into the PCB. A significant reduction in complexity results.
Other features and advantages of the invention will be apparent from the following detailed description, the accompanying drawings and the claims.